The present invention relates generally to pole supports, and more particularly, towards supports for overhead luminaries having tamper-proof mounting hardware. The invention also relates to pole supports which, in order to minimize bodily injury and property damage, are designed to break-away from the base when struck by a moving vehicle.
Each year, a substantial number of injuries and deaths, as well as property damage are incurred as a result of vehicles colliding with highway signs, traffic signals and overhead lighting. This is because of the strength of the pole itself and the resistance thereof to deformation in response to impact by a vehicle. It has been difficult to manufacture a pole with the requirements that it handle the necessary load for which it is designed, but at the same time, that it yield upon impact by a vehicle. In order to reduce the deleterious results of such impact, frangible supports are often specified that are designed to break-away when struck by a vehicle. The release mechanism for such break-away supports are typically plastic hinges, fracture elements, slip planes or a combination thereof.
Prior art break-away supports are expensive, difficult to install, and are typically unreliable in terms of having a predictable threshold for break-away under impact force. This means that in many instances, the base of prior art supports do not function to prevent the damage and injury they are designed to alleviate. There thus exists a need for highly reliable break-away pole supports that will function to break-away at the proper impact force, but will still resist other outside forces, such as wind loads.
Accordingly, one object of the present invention is to provide a new and improved break-away support for roadway poles.
Another object of the invention is to provide a new and improved break-away pole support that is easy to install and is reusable following impact by a moving vehicle.
Still another object is to provide a new and improved break-away support for roadway poles that requires a minimum number of parts and is reliable in operation.
Supports for roadway poles of which I am aware are typically mounted along a roadway by mounting a base on a poured concrete foundation with embedded anchor bolts. Then the pole is made perfectly vertical using shim stock to take up any irregularities. The base is anchored to the concrete foundation with nuts applied to the threaded bolts that extend through the base flanges on the lower part of the base. Besides detracting from the appearance of the support, the mounting hardware is exposed to possible vandalism. Furthermore, the hardware tends to corrode because of exposure to moisture, as well as collects dirt and debris thereby requiring maintenance. To prevent such conditions, costly covers have been found to be necessary.
Accordingly, another object of the invention is to provide a new and improved roadway pole support wherein mounting hardware is protected from vandalism and environmental moisture.
Another object is to provide a roadway pole support requiring minimum installation and maintenance labor.
The portion of the pole that is most apt to fracture is the lower end thereof at the pole support interface which absorbs stresses induced by external forces, such as wind, applied against the pole. The portion of the pole just above the support is further weakened during assembly as the pole and support are welded together as shown, for example, in U.S. Pat. No. 3,839,835 to Meyer, because welding tends to alter the structure of the metal forming the pole making it brittle. In order to increase the strength of the pole, the wall of the pole must be made relatively thick. The thick wall increases the weight of the pole, makes installation more difficult and drives up costs.
Still another object of the invention, therefore, is to reinforce the strength of the pole in the region of the pole support interface without substantially increasing the thickness of the pole wall.